President Barack Obama (R) and Republican presidential candidate Mitt Romney (L) arrive for the first presidential debate at Magness Arena at the University of Denver in Denver, Colorado, October 3, 2012. (SAUL LOEB/AFP/GettyImages)

DENVER — Mitt Romney emerged as the decisive winner of the first presidential debate with President Barack Obama on Wednesday night, a reality even the president’s surrogates were unable to spin.

No defining moments emerged from the debate, which lasted 90 minutes. The zingers from both sides were underwhelming. During the evening, the two candidates mainly wonked out and discussed their differences on everything from Medicare to taxes to deficit reduction.

But style, more than substance, led to Romney’s clear advantage. The former Massachusetts governor was aggressive, and he made his arguments without any sign of hesitation. He repeatedly asserted himself and even interrupted moderator Jim Lehrer occasionally to ensure that he could respond to the president’s remarks.

Obama, by contrast, seemed tentative. Where Romney launched straight to his answers, the president often stuttered and rambled, as though struggling to figure out what point he ought to make. Romney regularly directed his comments against the president, but Obama repeatedly turned to the American people to ask, “Does anybody out there think …?”

The president failed to land punches on health care, and he did not even mention Romney’s “47 percent” comments about the number of Americans who do not pay income tax, which were used to damning effect in a recent campaign ad.

After the debate, the spin room buzzed with reporters asking variations on the question, “Was Obama off his game?” (RELATED: Watch the debate here)

Surrogates for Romney were ebullient, while Obama campaign officials declared victory by retroactively lowered expectations for the debate, saying repeatedly often that Obama had done “what he needed to do” in the debate.

“Our goal was to speak to the American people,” said campaign press secretary Jen Psaki. “He turned and faced the American people at several points in the debate and said, ‘These are my policies, this is what I’m fighting for.'”

“I think he came in there knowing what job he had to do, and that was to communicate to people at home his detailed plans for moving the country forward … and I think he did that,” echoed deputy campaign manager Stephanie Cutter.

“I think the president did exactly what he did in his convention speech,” agreed campaign manager Jim Messina.

“We don’t believe in decisive moments,” said senior campaign adviser David Plouffe. A campaign, he said, was more about “telling a story over a period of time” through ads, speeches, debates and interviews.

Cutter acknowledged, though, that Romney had done well in the debate.

“I think Mitt Romney scores points on style,” she added, “and he clearly practiced that, but that’s not been his problem in this campaign.”

Cutter suggested that, while Romney had performed well, he had a higher bar to meet than the president.

“Mitt Romney needed to come in here tonight not just to win this debate — which, let’s face it, challengers normally do — he needed to change the dynamic of this race. He didn’t do that,” she said.

“This was a knockout,” said former New York Mayor Rudy Giuliani. “I’ve been to many presidential debates; I’ve never seen one as one sided as this one. Gov. Romney was on target; his facts, he was in great command of them; he was on the attack against President Obama. President Obama looked confused, he looked like he was searching for his teleprompter, he didn’t have it, and what he retreated to instead was an incomprehensible explanation of his Obamacare.”

“That’s the Mitt Romney I know and love,” said Ohio Sen. Rob Portman, who served as Romney’s debate partner, playing the part of the president.

Asked how the debate had gone, Rosario Marin, the United States Treasurer under former President George W. Bush, simply smiled and asked, “Can I jump up and down?”